1. Field of the Invention
The present invention relates to a novel organic compound and an organic light-emitting device using the same.
2. Related Background Art
An organic light-emitting device has a thin film containing a fluorescent compound interposed between an anode and a cathode, and utilizes light emitted when excitons of the fluorescent compound generated by injection of electrons and holes from each electrode returns to the ground state.
A research by Eastman Kodak Company in 1987 (Appl. Phys. Lett. 51, 913 (1987)) reports light emission of about 1000 cd/m2 at an applied voltage of about 10V in a separated-function two-layer structure device in which ITO is used for the anode, magnesium-silver alloy for the cathode, an aluminum quinolinol complex as an electron-transporting material and a light-emitting material, and a triphenylamine derivative as a hole-transporting material (U.S. Pat. Nos. 4,539,507, 4,720,432 and 4,885,211).
In addition, by changing the kind of fluorescent organic compounds, ultra-violet to infrared light can be emitted, and various compounds are now being actively studied (U.S. Pat. Nos. 5,151,629, 5,409,783 and 5,382,477, Japanese Patent Application Laid-Open Nos. H02-247278, H03-255190, H05-202356, H09-202878 and H09-227576).
Recently, a number of studies have been made on utilization of triplet energy for electroluminescence using a phosphorescent compound as a light-emitting material. A group in Princeton University has reported that an organic light-emitting device in which an iridium complex is used as a light-emitting material has high luminous efficiency (Nature, 395, 151 (1998)).
In addition to organic light-emitting devices using a low molecular weight material described above, an organic light emitting device using a conjugated polymer has been reported by a group in Cambridge University (Nature, 347, 539 (1990)). In this report, by forming a film of poly(phenylenevinylene) (PPV) in a coating system, light emission is found in a single layer. Patents related to organic light emitting devices using conjugated polymer include U.S. Pat. Nos. 5,247,190, 5,514,878 and 5,672,678, Japanese Patent Application Laid-Open Nos. H04-145192 and H05-247460.
As described above, recent development in organic light emitting devices is remarkable, and since they have features of high luminance at a low applied voltage, variety in emission wavelength and fast response, and since it is possible to fabricate thin and lightweight light emitting devices, they are expected to be used in a broad range of applications.
At present, however, light output of higher luminance or higher conversion efficiency is required. In addition, there are still many problems in durability such as degradation with the elapse of time due to long term use and use in ambient gas containing oxygen or moisture. Further, when application to full color displays is intended, light emission of blue, green and red with high color purity is required. However, there is no satisfactory solution for these problems and various proposals are now being made.
Examples of materials containing a benzene ring substituted by pyrene and organic light emitting devices using the same are described in Japanese Patent Application Laid-Open No. 2002-324678. However, although the application discloses that it provides a device excellent in luminescent properties and durability, the device has low external quantum efficiency, and there is no specific description of durability and lifetime.